There are numerous patents which describe liquid detergent compositions containing an amine oxide surfactant in combination with one or more other surfactants such as anionic surfactants. Some of these U.S. Pat. Nos. are 4,316,824; 4,435,317; 4,536,317; 4,536,318; 4,663,063; 4,599,188; 4,555,360; 5,118,440; 5,320,783; 5,417,893 and 5,415,814.
A major problem for a liquid detergent composition containing an amine oxide is color stability. Formulas containing amine oxide discolor upon aging due to heat or the ultraviolet rays of sunlight. Decomposition of the amine oxide accompanied by an increase in pH is also observed in these systems. The use of hydroxyethylethylenediaminetetraacetic acid (HEEDTA) as a chelant to improve color stability has only been marginally successful.
The present invention teaches that the pH and color stability of a liquid detergent composition containing amine oxides can be dramatically improved through the use of citric acid as a chelant in place of HEEDTA.
U.S. Pat. No. 3,935,129 discloses a liquid cleaning composition based on the alkali metal silicate content and containing five basic ingredients, namely, urea, glycerin, triethanolamine, an anionic detergent and a nonionic detergent. The silicate content determines the amount of anionic and/or nonionic detergent in the liquid cleaning composition. However, the foaming property of these detergent compositions is not discussed therein.
U.S. Pat. No. 4,129,515 discloses a heavy duty liquid detergent for laundering fabrics comprising a mixture of substantially equal amounts of anionic and nonionic surfactants alkanolamines and magnesium salts, and, optionally, zwitterionic surfactants as suds modifiers.
U.S. Pat. No. 4,224,195 discloses an aqueous detergent composition for laundering socks or stockings comprising a specific group of nonionic detergents, namely, an ethylene oxide of a secondary alcohol, a specific group of anionic detergents, namely, a sulfuric acid ester salt of an ethylene oxide adduct of a secondary alcohol, and an amphoteric surfactant which may be a betaine, wherein either the anionic or nonionic surfactant may be the major ingredient. The specific class of anionics utilized in this patent is the very same group of anionic detergents expressly excluded in present invention in order to eliminate the alkanol ethoxylate sulfation process and the potential dioxane toxicity problem. Furthermore, this patent finds heavily foaming detergents undesirable for the purpose of washing socks.
The prior art also discloses detergent compositions containing all nonionic surfactants as shown in U.S. Pat. Nos. 4,154,706 and 4,329,336 wherein the shampoo compositions contain a plurality of particular nonionic surfactants in order to effect desirable foaming and detersive properties despite the fact that nonionic surfactants are usually deficient in such properties.